The present invention relates to low compression, resilient golf balls and portions thereof formed from the conversion reaction of an amount of polybutadiene, a free radical source, and a cis-to-trans catalyst including at least one sulfur component, selenium component, or tellurium component, at a sufficient reaction temperature to form a polybutadiene reaction product.
Conventional golf balls can be divided into several general classes: (a) solid golf balls having one or more layers, and (b) wound golf balls. Solid golf balls include one-piece balls, which are easy to construct and relatively inexpensive, but have poor playing characteristics and are thus generally limited for use as range balls. Two-piece balls are constructed with a generally solid core and a cover and are generally the most popular with recreational golfers because they are very durable and provide maximum distance. Balls having a two-piece construction are commonly formed of a polymeric core encased by a cover. Typically, the core is formed from polybutadiene that is chemically crosslinked with zinc diacrylate and/or other similar crosslinking agents. These balls are generally easy to manufacture, but are regarded as having limited playing characteristics. Solid golf balls also include multi-layer golf balls that are comprised of a solid core of one or more layers and/or a cover of one or more layers. These balls are regarded as having an extended range of playing characteristics.
Wound golf balls are generally preferred by many players due to their high spin and soft xe2x80x9cfeelxe2x80x9d characteristics. Wound golf balls typically include a solid, hollow, or fluid-filled center, surrounded by a tensioned elastomeric material and a cover. Wound balls generally are more difficult and expensive to manufacture than solid two-piece balls.
A variety of golf balls designed to provide a wide range of playing characteristics, i.e., the compression, velocity, xe2x80x9cfeel,xe2x80x9d and spin, that can be optimized for various playing ability, are known in the prior art. One of the most common polymer components present in modern golf ball construction, in addition to ionomers, is polybutadiene and, more specifically, polybutadiene having a high cis- isomer concentration. The use of a polybutadiene having a high cis- concentration results in a very resilient and rigid golf ball, especially when coupled with a hard cover material. These highly resilient golf balls have a relatively hard xe2x80x9cfeelxe2x80x9d when struck by a club. Soft xe2x80x9cfeelxe2x80x9d golf balls constructed with a high cis-polybutadiene have low resilience. In an effort to provide improved golf balls, various other polybutadiene formulations have been prepared, as discussed below.
U.S. Pat. No. 3,239,228 discloses a solid golf ball having a core molded of polybutadiene rubber with a high sulfur content, and a cover. The polybutadiene content of the core is stereo-controlled to the configuration 25-100 percent cis- and 0-65 percent trans-1,4-polybutadiene, with any remainder having a vinyl configuration of polybutadiene. A preferred embodiment of the polybutadiene golf ball core contains 35 percent cis-, 52 percent trans-, and 13 percent vinyl-polybutadiene. The level of trans- and vinyl- content are disclosed to be unimportant to the overall playing characteristics of the polymer blend.
British Patent No. 1,168,609 discloses a molding composition from which improved golf ball cores can be molded and which contains cis-polybutadiene as a basic polymer component. The core polymer component typically includes at least 60 percent cis-polybutadiene, with the remainder being either the trans- or vinyl- forms of polybutadiene. In a preferred embodiment, the core polybutadiene component contains 90 percent cis- configuration, with the remaining 10 percent being either the trans- or vinyl- configurations of 1,4-polybutadiene.
U.S. Patent Nos. 3,572,721 and 3,572,722 disclose a solid, one- or two-piece golf ball, with the two-piece ball having a core and a cover. The cover material can include any one of a number of materials, or blends thereof, known to those of ordinary skill in the art, including trans-polybutadiene which may be present in an amount from at least 90 percent, with the remainder being the cis- and/or vinyl configuration.
British Patent No. 1,209,032 discloses a two- or three-piece golf ball having a core and a cover. The core or cover material can be any material capable of being crosslinked. In particular, the material can be a polymer or a copolymer of butadiene or isoprene. Preferably, the polymer component is polybutadiene having a cis content of greater than 50 percent by weight.
U.S. Pat. No. 3,992,014 discloses a one-piece, solid golf ball. The golf ball material is typically polybutadiene, with a stereo-configuration selected to be at least 60 percent cis-polybutadiene, with the remaining 40 percent being the trans-polybutadiene and/or 1,2-polybutadiene (vinyl) isomers.
U.S. Pat. No. 4,692,497 discloses a golf ball and material thereof formed by curing a diene polymer including polybutadiene and a metal salt of an alpha, beta ethylenically unsaturated acid using at least two free radical initiators.
U.S. Pat. No. 4,931,376 discloses a process for producing butadiene polymers for use in various applications, including golf ball cover materials. One embodiment of the invention employs a blended polymeric resin material, including at least 30 percent by weight of a trans-polybutadiene polymer as a golf ball cover on a two-piece ball. In a preferred embodiment, the golf ball cover material contains a blend including 30 to 90 percent by weight of a trans-polybutadiene polymer.
U.S. Pat. No. 4,971,329 discloses a solid golf ball made from a polybutadiene admixture of cis-1,4 polybutadiene and 1,2 polybutadiene, a metal salt of an unsaturated carboxylic acid, an inorganic filler, and a free radical initiator. The admixture has about 99.5 percent to about 95 percent by weight of cis-1,4 polybutadiene and about 0.5 percent to about 5 percent by weight of 1,2 polybutadiene.
U.S. Pat. No. 5,252,652 discloses a one-piece or multi-layered golf ball core with improved flying performance from a rubber composition comprising a base rubber, preferably 1,4-polybutadiene with a cis- content of at least 40 mole percent, an unsaturated carboxylic acid metal salt, an organic peroxide, and an organic sulfur compound and/or a metal salt thereof. The organic sulfur compound and/or a metal salt is typically present in an amount from about 0.05 to 2 parts per hundred by weight and the organic peroxide is typically present in an amount from about 0.5 to 3 parts per hundred by weight of the total polymer component.
European Patent No. 0 577 058 discloses a golf ball containing a core and a cover that is formed as two separate layers. The inner layer of the cover is molded over the core and is formed from ionomer resin. The outer layer of the cover is molded over the inner layer and is formed from a blend of natural or synthetic balata and a crosslinkable elastomer, such as polybutadiene. In one embodiment of the outer layer of the cover, the elastomer is 1,4-polybutadiene having a cis- structure of at least 40 percent, with the remaining 60 percent being the trans- isomer. A preferred embodiment contains a cis- structure of at least 90 percent and more preferably, a cis- structure of at least 95 percent.
U.S. Pat. No. 5,421,580 discloses a wound golf ball having a liquid center contained in a center bag, a rubber thread layer formed on the liquid center, and a cover over the wound layer and liquid center. The cover material can include any one of a number of materials, or blends thereof, known to those of ordinary skill in the art, including trans-polybutadiene and/or 1,2-polybutadiene (vinyl), such that the cover has a JIS-C hardness of 70-85; preferred trans- percentages are not disclosed.
U.S. Pat. No. 5,697,856 discloses a solid golf ball having a core and a cover wherein the core is produced by vulcanizing a base rubber composition containing a butadiene rubber having a cis-polybutadiene structure content of not less than 90 percent before vulcanization. The amount of trans-polybutadiene structure present after vulcanization is 10 to 30 percent, as amounts over 30 percent are alleged to detrimentally result in cores that are too soft with deteriorated resilience performance, and to cause a decrease in golf ball performance. The core includes a vulcanizing agent, a filler, an organic peroxide, and an organosulfur compound.
British Patent No. 2,321,021 discloses a solid golf ball having a core and a cover formed on the core and having a two-layered cover construction having an inner cover layer and an outer cover layer. The outer cover layer is comprised of a rubber composite that contains 0.05 to 5 parts by weight of an organic sulfide compound. The core rubber composition comprises a base rubber, preferably 1,4-polybutadiene having a cis- content of at least 40 percent by weight, a crosslinking agent, a co-crosslinking agent, an organic sulfide, and a filler. The crosslinking agent is typically an organic peroxide present in an amount from 0.3 to 5.0 parts by weight and the co-crosslinking agent is typically a metal salt of an unsaturated fatty acid present in an amount from 10 to 40 parts by weight. The organic sulfide compound is typically present from 0.05 to 5 parts by weight.
U.S. Pat. No. 5,816,944 discloses a solid golf ball having a core and a cover wherein the core has a JIS-C hardness of 50 to 80 and the cover has a Shore-D hardness of 50 to 60. The core material includes vulcanized rubber, such as cis-polybutadiene, with a crosslinker, an organic peroxide, an organosulfur compound and/or a metal-containing organosulfur compound, and a filler.
Additionally, conventional polymers that have a high percentage of the trans-polybutadiene conformation, such as DIENE 35NF, from Firestone Corp., that has 40 percent cis- isomer and 50 percent trans-polybutadiene isomer, and mixtures of high-cis- and high-trans-polybutadiene isomers, such as CARIFLEX BR1220, from Shell Corporation, and FUREN 88, from Asahi Chemical Co., respectively, typically do not yield high resilience values and therefore are not desirable. It is thus desired to prepare golf balls having lower compression, i.e., a softer ball, while having the same or higher resilience than conventional balls. It is alternatively desired to obtain the same or lower compression while achieving greater resilience.
All of the embodiments according to the invention below may be used in any golf ball. Particularly, each embodiment may be used in one of the three following embodiments. In the first such embodiment, the golf ball is a one-piece golf ball. In the second such embodiment, the golf ball includes a core and a cover disposed concentrically about the core and the reaction product is disposed in at least a portion of the core. In the third such embodiment, the golf ball includes a core having a center and at least one intermediate layer; and a cover disposed concentrically about the core, wherein the reaction product is disposed in a portion of the core.
The invention relates to a golf ball formed from the conversion reaction of an amount of polybutadiene, a free radical source, and a cis-to-trans catalyst including at least one Group VIA element at a sufficient reaction temperature to form a polybutadiene reaction product which includes an amount of trans-polybutadiene greater than the amount of trans-polybutadiene present before the conversion reaction. In one embodiment, the reaction product still includes a portion of the cis-to-trans catalyst including at least one elemental component. In one embodiment, the golf ball includes a cover having at least one of a dimple coverage of greater than about 60 percent, a hardness from about 35 to 80 Shore D, or a flexural modulus of greater than about 500 psi, and wherein the golf ball has at least one of a compression from about 50 to 120 or a coefficient of restitution of greater than about 0.7. In another embodiment, the reaction product has a first dynamic stiffness measured at xe2x88x9250xc2x0 C. that is less than about 130 percent of a second dynamic stiffness measured at 0xc2x0 C.
In one preferred embodiment, the Group VIA element includes a sulfur component of elemental sulfur, polymeric sulfur, or a combination thereof. In another embodiment, the Group VIA element includes selenium, tellurium, or a combination thereof. The cis-to-trans catalyst including a Group VIA element is typically present in an amount from about 0.01 to 25 parts per hundred of polybutadiene. In a preferred embodiment, the cis-to-trans catalyst is present in an amount from about 0.01 to 1 parts per hundred of polybutadiene. In a more preferred embodiment, the cis-to-trans catalyst is present in an amount from about 0.05 to 0.5 parts per hundred of polybutadiene. In another embodiment, the cis-to-trans catalyst is present in an amount sufficient to produce the polybutadiene reaction product so as to contain at least about 32 percent trans-polybutadiene isomer. In another embodiment, the cis-to-trans catalyst further comprises at least one of an inorganic sulfide compound, an organosulfur compound, an aromatic organometallic compound, a metal-organosulfur compound, or an aromatic organic compound.
In one embodiment, the polybutadiene reaction product includes less than about 7 percent vinyl isomer content based on the total polybutadiene. In a preferred embodiment, the polybutadiene reaction product includes less than about 4 percent vinyl isomer. In a more preferred embodiment, the polybutadiene reaction product includes less than about 2 percent vinyl isomer.
In another embodiment, the reaction product further includes a vulcanization accelerator, preferably in an amount sufficient to facilitate cis-to-trans conversion. In a preferred embodiment, the vulcanization accelerator includes at least one of sulfenamide, thiazole, dithiocarbamate, thiuram, xanthate, thiadiazine, thiourea, guanadine, or aldehydeamine. The accelerator is typically present in an amount from about 0.05 to 2 phr. In a preferred embodiment, the accelerator is present in an amount from about 0.1 to 1 phr.
In one embodiment, the portion of the core having the reaction product is the center. In another embodiment, the center includes a fluid. In yet another embodiment, the intermediate layer may include a wound layer of tensioned elastomeric material. In a preferred embodiment, the tensioned elastomeric material includes the reaction product. In another embodiment, the golf ball further includes a density-modifying filler.
The invention also relates to a method for forming a golf ball which includes combining (a) at least one of a cis-to-trans catalyst including at least one Group VIA element, (b) a free radical source, (c) a first resilient polymer component having a cis-polybutadiene component present in an amount greater than about 70 percent of the total polymer component, and optionally, (d) a crosslinking agent, converting a portion of the first resilient polymer component to a second resilient polymer component, wherein at least a portion of the cis-polybutadiene component is converted to a trans-polybutadiene component and wherein the polybutadiene in the second resilient polymer component is at least about 10 percent trans-polybutadiene and less than about 7 percent vinyl-polybutadiene, and forming the second resilient polymer component into at least a portion of the golf ball.
In one embodiment, the portion of the second resilient polymer component is formed into a solid sphere. In another embodiment, which may be alternative or in addition to the forming of the sphere, the portion may be formed into at least one layer disposed about the solid sphere. In the alternative embodiment, the sphere is formed but the portion is disposed in at least one layer disposed about the sphere. In the additive embodiment, an additional portion of the second resilient polymer component is formed into a cover disposed concentrically about a sphere.
In one embodiment, the polybutadiene component includes cis-polybutadiene present in an amount of at least 80 percent of the total first resilient polymer component. In another embodiment, a density-modifying filler is also included in the combining step. In yet another embodiment, the steps of combining the first resilient polymer component and the cis-to-trans catalyst and forming the portion, includes forming a sphere having a midpoint having a first amount of trans-polybutadiene and a surface having a second amount of trans-polybutadiene, wherein the first amount is at least about 6 percent less than the second amount.
In one embodiment, a portion of the sphere comprises a fluid. In another embodiment, a tensioned elastomeric material is wound about the sphere. In a preferred embodiment, the tensioned elastomeric material includes a reaction product including polybutadiene or polyisoprene and a cis-to-trans catalyst that includes the Group VIA elemental component.
In yet another embodiment, the forming includes single- or multi-step compression molding of the first resilient polymer component to convert the first resilient polymer component to the second resilient polymer, and forming the second resilient polymer component into a solid sphere. In a preferred embodiment, the compression molding takes 8 to 15 minutes. In a preferred embodiment, the converting and forming are substantially simultaneous.
The invention also relates to a golf ball prepared by a process which includes combining (a) at least one of a cis-to-trans catalyst including at least one Group VIA element, (b) a free radical source, and (c) a first resilient polymer component including a cis-polybutadiene component present in an amount greater than about 70 percent of the resilient polymer component, converting a portion of the first resilient polymer component to a second resilient polymer component in about 5 to 18 minutes, wherein at least a portion of the cis- isomer content is converted to a trans- isomer content and wherein the polybutadiene in the second resilient polymer component is at least about 10 percent trans-polybutadiene and less than about 7 percent vinyl-polybutadiene, and forming the second resilient polymer component into at least a portion of the golf ball.
The invention further relates to a golf ball including a material formed from the conversion reaction of a sufficient amount of polybutadiene, a free radical source, and a cis-to-trans catalyst including at least one Group VIA element, which reaction occurs at a sufficient temperature to form a polybutadiene reaction product which includes an amount of trans-polybutadiene greater than the amount of trans-polybutadiene present before the conversion reaction, wherein the reaction product includes a sphere which has a midpoint having a first hardness and a surface having a second hardness such that the second hardness differs from the first hardness by greater than 10 percent of the first hardness. In one embodiment, the reaction product still includes a portion of the cis-to-trans catalyst.
The golf ball may be prepared by combining at least (a) a cis-to-trans catalyst including at least one Group VIA element, (b) a free radical source, and (c) a first resilient polymer component including a cis-polybutadiene component present in an amount greater than about 70 percent of the total polymer, converting a portion of the first resilient polymer component to a second resilient polymer component in about 5 to 18 minutes at a sufficient temperature to convert at least a portion of the cis-polybutadiene component to a trans-polybutadiene component and wherein the polybutadiene in the second resilient polymer component is at least about 10 percent trans-polybutadiene and less than about 7 percent vinyl-polybutadiene, and forming the second resilient polymer component into at least a portion of the golf ball, wherein the second resilient component includes a sphere which has a midpoint having a first hardness and a surface having a second hardness such that the second hardness differs from the first hardness by greater than 10 percent of the first hardness.
The golf ball may also be prepared by combining at least (a) a cis-to-trans catalyst including at least one Group VIA element, (b) a free radical source, and (c) a first resilient polymer component including a cis-polybutadiene component present in an amount greater than about 70 percent of the total polymer component, converting a portion of the first resilient polymer component to a second resilient polymer component in about 5 to 18 minutes at a sufficient temperature to convert at least a portion of the cis-polybutadiene component to a trans-polybutadiene component and wherein the polybutadiene in the second resilient polymer component is at least about 10 percent trans-polybutadiene and less than about 7 percent vinyl-polybutadiene, and forming the second resilient polymer component into at least a portion of the golf ball, wherein the second resilient component has a first dynamic stiffness measured at xe2x88x9250xc2x0 C. that is less than about 130 percent of a second dynamic stiffness measured at 0xc2x0 C.